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SUMMARY:SUPERCHIRALITY AND BLOCH SURFACE WAVES - Prof. Paolo Biagioni\, Ph
 ysics Department\, Politecnico di Milano (IT)
DTSTART:20190124T150000Z
DTEND:20190124T160000Z
UID:TALK113716@talks.cam.ac.uk
CONTACT:Lingtao Kong
DESCRIPTION:Circular dichroism (CD) spectroscopy is one of the most releva
 nt tools for the discrimination of enantiomers and for the determination o
 f their configuration and conformation. However\, CD signals are extremely
  weak\, making the analysis of small amounts of chiral analytes very chall
 enging. Recently\, novel ‘superchiral’ approaches have been proposed t
 o enhance the CD signal by tailoring the properties of the electromagnetic
  field through the control of the associated optical chirality. In this fr
 amework\, plasmonic chiral sensing holds exciting perspectives but several
  limitations have also been discussed.\nIn this talk we first introduce a 
 universal limit to plasmonic superchirality\, demonstrating that in the qu
 asi-static approximation the average optical chirality in the surrounding 
 of a plasmonic nanostructure is analytically bound and the upper limit pos
 es significant challenges in the visible spectral range [1]. These finding
 s also justify recent proposals to move to dielectric materials for superc
 hiral spectroscopies. Along this line\, we introduce the concept of ‘sup
 erchiral surface waves’ originating from the coherent superposition of t
 he TE and TM surface modes in a one-dimensional photonic crystal with an a
 nisotropic metamaterial surface defect [2\,3]. The resulting platform prov
 ides superchiral fields over arbitrarily large areas and wide spectral ran
 ges (up to the UV)\, with CD signal enhancements of more than 2 orders of 
 magnitude. Moreover\, the original spectral fingerprint associated with a 
 specific CD resonance is reconstructed with high fidelity. These findings 
 pave a possible way towards on- chip surface-enhanced chiral sensing\, spe
 ctroscopy\, and all-optical manipulation [2-4].\n
LOCATION:Pfizer Lecture Theatre\, Department of Chemistry
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